This invention relates to protective and decorative coatings for articles, particularly titanium or titanium alloy articles.
It is currently the practice with various brass articles such as lamps, trivets, candlesticks, door knobs, door handles, door escutcheons and the like to fist buff and polish the surface of the article to a high gloss and to then apply a protective organic coating, such as one comprised of acrylics, urethanes, epoxies, and the like, onto this polished surface. While this system is generally satisfactory it has the drawback that the buffing and polishing operation, particularly if the article is of a complex shape, is labor intensive. Also, the known organic coatings are not always as durable as desired, particularly in outdoor applications where the coated articles are exposed to the elements and ultraviolet radiation.
This disadvantage has been remedied by applying a physical vapor deposited coating including a refractory metal nitrogen containing compound wear resistant layer. U.S. Pat. Nos. 5,667,904; 5,478,660, inter alia, describe such a coating. This coating has a brass color and includes at least one nickel basecoat deposited directly on the surface of the coated article. The nickel basecoat is deposited by plating. U.S. Pat. Nos. 6,399,219 and 6,391,457 describe vapor deposited coatings containing a polymeric basecoat.
It would be very advantageous if a coating could be provided which had a dark copper color and did not require the nickel or polymeric basecoat, as this would eliminate a cumbersome and expensive plating or polymeric deposition operation. The present invention attains these objectives, particularly with a titanium or titanium alloy substrate.
The present invention is directed to an article or substrate, particularly a metallic article such as stainless steel or titanium, having a multi-layer coating on at least a portion of its surface. The article has deposited on its surface a coating comprised of strike layer of chromium, refractory metal or refractory metal alloy such as titanium-zirconium alloy, over the strike layer is a color layer comprised of titanium-zirconium alloy nitride or carbonitride, over the color layer is deposited a zirconium-titanium alloy oxide or zirconium-titanium alloy oxynitride. The coating is decorative and also provides corrosion resistance and wear resistance. The coating provides the appearance or color of dark copper, i.e., has a dark copper color tone. Thus, an article surface having the coating thereon has a dark copper color with a highly polished or textured surface.
The first layer deposited directly on the article or substrate is an adhesion promoting or strike layer comprised of a metal, preferably chromium, refractory metal or refractory metal alloy. Over the strike layer is an opaque color layer comprised of a titanium-zirconium alloy nitride or carbonitride. This color layer is important to the color of the final product. The top layer is a semi-transparent layer comprised of a titanium-zirconium oxide or titanium-zirconium oxynitride.
The strike layer and color layer are preferably applied by a vapor deposition such as physical vapor deposition or chemical vapor deposition.